Marlene Zuk Interview in New Scientist

New Scientist, June 20, 2007

The Joy of Parasites
by Peter Aldhous

While grim tales of coming plagues engage the popular imagination, biologist Marlene Zuk is focusing on the bright side of disease. Pathogens aren’t always our enemies, she says; in fact, they have helped shape our evolutionary history. As Zuk tells Peter Aldhous we ought to respect our complex – and sometimes comical – relationship with pathogens and parasites.

"You call for greater appreciation of pathogens. What is there to appreciate?
This is somewhat tongue-in-cheek. We need to appreciate them not in the sense of praising, but in the sense of understanding the impact of parasites – and I include viruses, bacteria and fungi. When you take an art appreciation course, no one expects that you’re going to love all the paintings, but you’re going to see how art has affected life. Similarly, if you’re going to appreciate disease, you need to understand how it has affected life. It doesn’t mean you’re going to love diseases, or that you’re going to think it’s great to be sick.

Why have parasites and pathogens been such a powerful force in our evolution?
Because of the potential for co-evolution. When selection acts to produce an animal that is able to resist a drought, it leaves more offspring, and so you end up with a population that has, say, skin that is less likely to desiccate. But that doesn’t provoke the environment into becoming even drier. On the other hand, if defence against a disease evolves, there is selection pressure on the disease organism to evolve back. The tuberculosis bacterium might become better at penetrating your lungs, if your lungs have evolved a mechanism for resisting their entry.

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